The techniques disclosed herein relate to attachment structures configured to attach a first member to a second member, and lens units which include a conversion lens and an intermediate ring.
There have been various types of structures configured to attach a first member to a second member, such as a structure in which a first member is attached to a second member by relatively rotating the first member and the second member in a circumferential direction about an axis.
For example, Japanese Patent Publication No. 2000-235222 discloses a lens unit configured to attach a conversion lens as a first member to an adaptor as a second member. Specifically, an external thread is formed at a back end of the conversion lens, and an internal thread is formed at a front end of the adaptor. The conversion lens is attached to the adaptor by relatively rotating the conversion lens and the adaptor and screwing the external thread and the internal thread.